Easily maintainable gas turbine engine

ABSTRACT

A differential gas turbine engine is constructed so that the power module may be removed as a unit from the output gearbox. Additional features enable major hot section components to be removed for inspection or replacement without major disassembly of the engine.

11111te States Cronstedt 1 51 Sept. 25, 1973 [75] Inventor:

Val Cronstedt, Williamsport, Pa.

Avca Corporation, Williamsport, Pa.

Filed: Mar. 20, 1972 Appl. No.: 236,031

Assignee:

2,709,567 5/1955 Wood 415/407 2,822,974 2/1958 Mueller 417/407 2,839,0056/1958 Means 417/407 3,172,260 3/1965 Chute 1 415/122 3,269,317 8/1966Lattanzio et al.... 415/122 3,505,816 4/1970 Wilde 415/122 3,632,2221/1972 Cronstedt 415/122 Primary Examiner-C. J. Husar Att0rr1ey-CharlesM. Hogan et a1.

[52] US. Cl 417/407, 415/122, 415/201,

415/360, 415/DIG. 001, 417/373 [57] ABSTRACT 51 l. l. E E Search 417/40:A differential gas turbme engme 1s constructed so that the power modulemay be removed as a unit from the output gearbox. Additional featuresenable major hot [56] References Cited section components to be removedfor inspection or replacement without major disassembly of the engine.UNITED STATES PATENTS 3,271,949 9/1966 Jones et al. 415/122 13 Claims, 1Drawing Figure 2,650,060 8/1953 Stalker 415/122 Z6 90 I58 A6 C 58, 4m /274 86 ya we Q? /64 52 90k 42 ill? 2 2 24 06 "2 L34 58 744 1 /!0 /a w I22 60 w 34 62 I00 Ii EASILY MAINTAINABLE GAS TURBINE ENGINE The presentinvention relates to gas turbine engines and more particularly tostructural features of these engines.

It is a common object in the gas turbine art to provide engines thatallow reasonable accessibility to components of the engine that requirefrequent inspection and/or maintenance. This is particularly true ofsmall gas turbine engines where the overall reduced size of the enginemakes it important to provide a high degree of accessibility.

Therefore it is an objective of the present invention to provide a gasturbine engine structure allowing that high degree of maintainabilitywithout major disassembly of the engine.

The objective is achieved by a gas turbine engine which comprises anoutput gearbox having an aft cover; a frame structure that has a forwardring abutting the aft cover of the gearbox housing and an aft ringspaced from the forward ring. A power module includes a main supportstructure abutting the aft ring of the frame structure and has an outerhousing abutting the main support structure. Means are provided forreleasably connecting the gearbox housing, aft cover and forward ring,permitting selective removal of the gearbox from the power modulewithout disconnecting the gearbox housing and the aft cover. Means arealso provided for releasably connecting the aft ring, main supportstructure and outer housing, permitting selective removal of the outerhousing without disconnecting the aft ring and the main supportstructure.

The above and other related objectives and features of the presentinvention will be apparent from a reading of the description of thedisclosure shown in the accompanying drawing and the novelty thereofpointed out in the appended claims.

The single FIGURE illustrates a longitudinal sectional view of a gasturbine engine embodying the present invention.

Referring to the drawing, there is shown a gas turbine engine comprisingan output gearbox module 12, a power module 14 interconnected by a framestructure 16. The gearbox module comprises an outer generally annularhousing 18 having a forward cover and bearing assembly 20 journaling apower output shaft 22. An aft cover 24 is secured to the housing 18 by aseries of jury screws 26 (only one of which is shown). The heads ofscrews 26 are flush with the aft surface of cover 24 and threaded intothe aft end of housing 18. Aft cover 24 has an outer flange 28 that mayprovide a primary mounting for the engine by a suitable arrangement,such as through holes 30, only one of which is shown.

A series of planet gears 32 (only one shown) are journaled on one sidein a rotatable carrier 34, integral with output shaft 22 and on theother side in a rotatable carrier 36 secured to carrier 34 and journaledin bearing assemblies 38 and 37. Bearing assembly 38 is mounted in afixed carrier 40 secured to the aft cover 24.

Planet gears 32 mesh with a turbine input gear 42 integral with aturbine input shaft 44 extending through opening 46 in the aft cover 24.A first ring gear 48 meshes with the planet gears 32 and connects with asecond ring gear 50 through a conical structure 52.

Ring gear 50 meshes with a series of fixed planets 54 (only one of whichis shown), suitably journaled in fixed carrier 40 on one side and theaft plate 24 on the opposite side. Planets 54 mesh with a compressorinput gear 55 integral with shaft 56.

Shaft 56 is coaxial with and telescoped over the turbine input shaft 44.Shaft 56 connects through a splined connection 58 with a compressorrotor shaft 60 journaled in a bearing assembly 62 which is secured to aforward annular support structure 64. Support structure 64 has an outerflange 66 which abuts the aft end of the cover 24.

The frame assembly 16 comprises a forward ring 68 which is connected tothe flange 66 by a series of jury screws 70 having their heads flushwith the forward face of flange 66. The bolts 72 releasably secure thesubassemblies of the housing 26, aft cover 24 and the flanges 66, 68. Aseries of structural V-struts 74 (only a portion of which are shown)extend from the forward ring 68 to an aft ring 76.

A main generally annular support structure, indicated by referencecharacter 78, has an outer flange abutting the aft face of ring 76. Aseries of jury screws 82 releasably secure the flange 80 to ring 76. Theheads of the jury screws 82 are flush with the aft face of outer flange80.

A radially extending cover 84 extends inward from outer flange 80 andprovides a forward support for a series of diffuser vanes 86 adapted toreceive air discharged from a centrifugal bladed impeller 88 secured onrotor shaft 60. An annular bell-mouthed shroud 90 is secured against anopening 92 in a cover 84 to provide an outer shroud for the compressorimpeller and also to form an inlet in combination with the forwardsupport structure 64. An annular flange 94 is secured to the aft ends ofthe diffuser vanes 86 and has an integral inwardly extending conicalsupport 96 extending to an integral bearing support sleeve 98.

A bearing assembly .100 is telescoped into the forward end of bearingsupport sleeve 98 and is held against a shoulder 102 by a threadedelement 104 that also functions as a seal. The compressor rotor shaft 60is held in bearing assembly by a spring clip 106, the removal of whichpermits the compressor rotor shaft to be pulled from the bearingassembly 100 in a forward direction. i Y

The aft end'of bearing support sleeve 98receives a bearing assemblywhich .is held against a shoulder 112 by a threaded nut and sealassembly 114. Nut and seal assembly 114 is adapted to be unthreaded frombearing support sleeve 98 by a suitable tool engaging it from a radiallyoutward position. Bearing assembly 1 10 is telescoped over a turbineshaft 118 which extends through the compressor rotor shaft 60 andconnects with turbine output shaft 44 at a splined connection 120.

A bladed radial inflow turbine wheel 122 is integral with and positionedon the aft end of turbine output shaft 118. Turbine wheel 122 has aseries of blades 124 receiving a hot gas stream from a nozzle assembly,generally indicated by reference character 126. The inlet nozzleassembly 126 comprises first and second radially extending walls 128 and130, respectively, at opposite ends of a series of nozzle vanes 132. Anannular turbine shroud element 134 extends from wall and surrounds theperiphery of the turbine blades 124. A conical support 136 extends fromwall 128 and has a flange 138 abutting a flange 140 on a conical element142 extending from element 94. A V-clamp assembly 144 releasably holdsthe flanges 138 and 140 together.

A segmented annular shroud 146 is positioned adjacent to the back sideof the turbine blades 124 and has a flange 148 sandwiched betweenflanges 140 and 138. The shroud 146 may be in a number of segments but aminimum two segments to permit its radial removal when the turbinenozzle assembly 126 is removed.

A turbine inlet duct 150 having a radially inward directed annularoutlet 152 is secured to walls 128 and 130. As shown in the FIGURE, theperiphery of wall 130 is radially inward of the periphery of wall 128 topermit removal of duct 150 in an aft direction. Turbine inlet duct 150receives a hot gas stream from a suitable combustor, not shown to aid indiscussion of the present invention. The combustor may be in an annularform in which a hot gas stream is generated in an annular perforatedchamber through the mixture of fuel and pressurized air. Alternatively,the combustor may be in a tangential form, indicated by phantom lines154, in which a perforated can having a single outlet discharging gasestangentially into the turbine inlet duct 150. Whatever combustor form isselected is fed from air discharged from the compressor diffuser vanes86 via an outer housing 156 which has a forward radial flange 158abutting the aft face of the radial flange 80 of the main structuresupport 78. A series of screws 160 are threaded into and releasablysecure flange 158 to the subassembly ofthe outer flange 80 and theforward ring 76.

The aft end of outer housing 156 has an opening 162 with a ring 164surrounding it. An annular divergent turbine diffusing outlet duct 166has a radial flange 168 abutting the aft end of housing 156. A series ofscrews 176 threaded into ring 164 holds flange 168 in place. The forwardend of duct 166 telescopes into and is piloted by a lip 172 integralwith the shroud 134 for the turbine.

The engine described operates as a differential gas turbine engine inwhich the compressor rotor, turbine rotor and output shaft areinterconnected by means of the differential gears in the gearboxassembly 12. For a discussion of the operating characteristics of thistype of engine, reference may be had to the issued US. Pat. Nos.2,693,080 and 2,804,748 in the name of David W. Hutchinson, entitledDifferential Gas Turbine and Gas Turbine with Clutch Control",respectively.

The engine described above embodies a number of features that enable ahigh degree of accessibility of the components without total disassemblyof the engine. If it is desired to remove the main gas generator module14 and frame structure 16 from the gearbox module 12, threadedassemblies 72 are removed and the gearbox module 12 is removed so as toseparate flange 66 and cover 24. It should be noted that the jury screws26 and 70 maintain the structural integrity of the separated components.The splined connections 58 and 120 enable the respective shafts to bereadily detached from one another.

After any fuel nozzle and combustor disassembly that may be necessary,the removal of the bolts 160 enables the outer housing 156 and exhaustduct 166 to be removed from the engine. This is done without affectingthe structural integrity ofthe main support structure 78 and framestructure 16 because of the jury screws 82. it is pointed out thatremoval of the outer housing 156 and the additional hot sectioncomponents described below can be accomplished without removing thegearbox module 12 from the frame 16 and power module 14. Thus, theseinspections and/or replacements can take place while the engine ismounted in place on the unit it is powering.

Removal of the outer housing 156 permits the outer surface of theturbine inlet duct 150 to be inspected. The turbine inlet duct 150 maybe removed from the engine in an aft direction. Since the walls 128 and130 are at different heights, this may be done without disturbing theturbine inlet nozzle assembly 126.

Upon removal of the V-clamp 144 the turbine inlet nozzle assembly 126and shroud 134 may be removed in an aft direction. It should be notedthat the flange 138 is positioned radially outward from the tip of theturbine blades 124 to permit removal in an aft direction without theneed to disconnect the turbine wheel 122. With the turbine inlet nozzleremoved the split shroud ring 146 may be removed to expose the innerportion of the engine. At this point it should be noted that a majorportion of the hot section components have been removed from the enginefor inspection and the turbine wheel is exposed for a completeinspection without disturbing the bearing connections for any of therotating components of the engine.

If it is desired to remove the turbine wheel 122, nut and seal element114 is unthreaded from bearing support sleeve 98, thus permitting theturbine wheel 122 and turbine shaft 118 to be removed rearward from theengine. At this point a new turbine wheel may be readily installedwithout disturbing the bearing assembly for the compressor. If it isdesired to remove the compressor impeller 88 or bearing assembly 100,the engine must be disassembled to the following condition: gearboxmodule 12 removed from frame, outer housing 156, turbine inlet duct 150,inlet nozzle 126, shroud 146, and turbine wheel 122 removed.

At this point the forward annular support structure 64 is disconnectedfrom forward ring 68 by removing jury screws 70. The annular support 64is then removed in a forward direction. Shroud is removed from cover 84,it being noted that opening 92 is radially outward from the periphery ofcompressor impeller 88. This exposes the compressor impeller forinspection and/or removal. The compressor impeller is simply removed byremoving the spring clip 106 which permits the compressor rotor shaft 60to be pulled out of the bearing assembly in a forward direction. Thebearing assembly 100 may be removed by unthreading the nut and sealassembly 104. Building up of the engine may be accomplished in thereverse order.

The engine structure described above permits a high degree ofaccessibility to the important hot section components of the enginewithout major disassembly or disturbing any of the bearing connections.This enables repair both in the field and in the shop to take place morereadily, while insuring that the running clearances will not bedisturbed.

The engine structure shown above has been described particularly inconnection with an engine of the differential type. It should beapparent to those skilled in the art that with some modification it maybe improved with equal success to gas turbine engines that are not ofthis type.

Accordingly, what is claimed as novel and desired to be secured byLetters Patent of the United States is:

l. A gas turbine engine structure comprising:

an output gearbox including a housing, at least one splined input shaftand an aft cover abutting the aft ring abutting the aft cover of saidgearbox housing, 7

an aft ring abutting the main support structure of said power module anda plurality of struts extending between and structurally interconnectingsaid rings thereby permitting air to pass to said inlet;

means for releasably connecting said gearbox housing, aft cover andforward ring permitting selective removal of said gearbox from saidengine without disconnecting said housing and said aft cover; and

means for releasably connecting said aft ring, main support structureand outer housing permitting selective removal of said outer housingwithout disconnecting said aft ring and said main support structure.

2. A gas turbine engine structure as in claim 1 wherein said aft coverof said gearbox has a flange extending radially outward from saidhousing, said flange providing a primary mount for said engine.

3. A gas turbine engine structure as in claim 1 further comprising aforward generally annular support structure for journaling said rotorwithin said frame structure, said forward support structure beingsandwiched between said aft cover and said forward ring, said forwardsupport structure being releasably secured to said forward ring so as topermit removal from said aft cover without disconnecting said forwardsupport structure from said forward ring.

4. A gas turbine engine structure as in claim 1 wherein said gasgenerator module comprises:

. a bladed radial inflow turbine wheel positioned on the aft end of saidrotor;

an annular turbine inlet nozzle and shroud surrounding the periphery ofsaid turbine wheel for directing a hot gas stream in a generally inwarddirection relative to said turbine;

an annular turbine inlet duct directing gases into said turbine inletnozzle and shroud,- said turbine inlet duct being removable from saidturbine inlet nozzle in an aft direction whereby it may be removed whensaid outer cover is removed; and

said turbine inlet nozzle and shroud being secured to said annularsupport structure radially outward from the tip of said turbine wheel sothat said nozzle and shroud may be removed in an axial direction withoutremoval of said turbine wheel.

5. A gas turbine engine structure as in claim 4 further comprising anannular shroud positioned forward of said turbine wheel, said shroudbeing sandwiched between said annular support structure and said turbinenozzle and split in segments whereby removal of said turbine nozzleenables removal of said shroud in a radial direction without removal ofsaid turbine wheel.

6. A gas turbine engine structure as in claim 1 wherein: i

said gas generator module has first and second independently rotatablerotors, the first rotor being telescoped over the second and both rotorshaving splined output shafts, said module comprising a compressorpositioned on said first rotor in the forward portion of said gasgenerator module and journaled by said main support structure, and aturbine positioned on said second rotor and journaled aft of saidcompressor by said main support structure;

said output gearbox comprises an output shaft and a pair of coaxialinput shafts connected to each other and to said output shaft through adifferential gearing, said input shafts being splined to connect withsaid compressor shaft and said turbine shaft, respectively.

7. A gas turbineengine structure as in claim 6 further comprising:

a bearing assembly telescoped over and fixed on said turbine shaft, saidbearing assembly being telescoped into said main support structure froman aft direction;

a retaining nut threaded into said main support structure for holdingsaid bearing assembly therein, said threaded element being rotatablefrom a radial direction whereby said turbine rotor may be removedwithout disturbing said compressor.

8. A gas turbine engine structure as in claim 7 further comprising acompressor bearing telescoped into the forward portion of said mainsupport structure, said compressor rotor being telescopable into saidcompressor bearing from a forward direction; and

a retaining clip restraining forward movement of said compressorrelative to said compressor bearing assembly whereby said retaining clipmay be removed when said turbine rotor'is removed to permit forwardremoval of said compressor rotor from said main support structure.

9. A gas turbine engine structure as in claim 8 wherein said compressorbearing is telescopable against a shoulder in said main supportstructure from a forward direction and is held therein by a threadedelement.

10. A gas turbine engine structure as in claim 9 wherein said turbine isa centripetal turbine having radially extending blades and said gasgenerator module comprises:

a turbine inlet nozzle and shroud surrounding the periphery of saidturbine for directing gases inward across the blades of said turbinewheel;

an annular turbine inlet duct connecting with said inlet nozzle fordirecting a flow of hot gases therethrough;

said turbine inlet duct being removable in an aft direction withoutdisassembly of said inlet nozzle and said inlet nozzle and shroud beingsupported from said annular support structure radially outward of thetip of said blades to permit removal thereof without removal of saidturbine.

11. A gas turbine engine structure as in claim 10 further comprising anannular heat shield positioned adjacent the back face of said turbine,said heat shield being sandwiched between said annular support structureand said inlet nozzle and being split whereby removal of said inletnozzle permits said heat shield to be removed in a radial directionwithout disassembly of said turbine.

7 8 12. A gas turbine engine structure as in claim 11 furwherein saidreleasable connecting means comprises: ther comprising: a series of juryscrews connecting only said aft cover a forward annular supportstructure positioned and said gearbox housing;

within said frame structure and journaling the fora series of juryscrews connecting said forward supward portion of said compressor rotor,said forport structure and said forward ring; ward annular supportstructure being sandwiched a series of jury screws connecting saidannular supbetween said gearbox module aft cover and said port structureand said aft ring; forward ring; and a first set of threaded assembliessandwiching the means for releasably connecting said forward annulargearbox housing, the aft cover and the forward ansupport structure tosaid forward ring so that said 0 nular support structure, the forwardring; and gearbox may be removed from said engine without a second setof threaded assemblies sandwiching said disconnecting said forwardannular support strucaft ring, said annular support structure and saidture and said forward ring. outer housing. 13. A gas turbine enginestructure as in claim 12

1. A gas turbine engine structure comprising: an output gearboxincluding a housing, at least one splined input shaft and an aft coverabutting the aft end of said gearbox housing, said cover having anopening through which said input shaft extends; a gas generator moduleincluding a generally annular main support structure, an outer housingabutting said main support structure, and at least one rotor journaledby said annular support structure and including a splined output shaftcoaxial with and releasably connectable with said gearbox input shaft,said gas generator module having an annular air inlet surrounding saidoutput shaft; a frame structure positioned between said gearbox and gasgenerator module and including: a forward ring abutting the aft cover ofsaid gearbox housing, an aft ring abutting the main support structure ofsaid power module and a plurality of struts extending between andstructurally interconnecting said rings thereby permitting air to passto said inlet; means for releasably connecting said gearbox housing, aftcover and forward ring permitting selective removal of said gearbox fromsaid engine without disconnecting said housing and said aft cover; andmeans for releasably connecting said aft ring, main support structureand outer housing permitting selective removal of said outer housingwithout disconnecting said aft ring and said main support structure. 2.A gas turbine engine structure as in claim 1 wherein said aft cover ofsaid gearbox has a flange extending radially outward from said housing,said flange providing a primary mount for said engine.
 3. A gas turbineengine structure as in claim 1 further comprising a forward generallyannular support structure for journaling said rotor within said framestructure, said forward support structure being sandwiched between saidaft cover and said forward ring, said forward support structure beingreleasably secured to said forward ring so as to permit removal fromsaid aft cover without disconnecting said forward support structure fromsaid forward ring.
 4. A gas turbine engine structure as in claim 1wherein said gas generator module comprises: a bladed radial inflowturbine wheel positioned on the aft end of said rotor; an annularturbine inlet nozzle and shroud surrounding the periphery of saidturbine wheel for directing a hot gas stream in a generally inwarddirection relative to said turbine; an annular turbine inlet ductdirecting gases into said turbine inlet nozzle and shroud, said turbineinlet duct being removable from said turbine inlet nozzle in an aftdirection whereby it may be removed when said outer cover is removed;and said turbine inlet nozzle and shroud being secured to said annularsupport structure radially outward from the tip of said turbine wheel sothat said nozzle and shroud may be removed in an axial direction withoutremoval of said turbine wheel.
 5. A gas turbine engine structure as inclaim 4 further comprising an annular shroud positioned forward of saidturbine wheel, said shroud being sandwiched between said annular supportstructure and said turbine nozzle and split in segments whereby removalof said turbine nozzle enables removal of said shroud in a radialdirection without removal of said turbine wheel.
 6. A gas turbine enginestructure as in claim 1 wherein: said gas generator module has first andsecond independently rotatable rotors, the first rotor being telescopedover the second and both rotors having splined output shafts, saidmodule comprising a compressor positioned on said first rotor in theforward portion of said gas generator module and journaled by said mainsupport structure, and a turbine positioned on said second rotor andjournaled aft of said compressor by said main support structure; saidoutput gearbox comprises an output shaft and a pair of coaxial inputshafts connected to each other and to said output shaft through adifferential gearing, said input shafts being splined to connect withsaid compressor shaft and said turbine shaft, respectively.
 7. A gasturbine engine structure as in claim 6 further comprising: a bearingassembly telescoped over and fixed on said turbine shaft, said bearingassembly being telescoped into said main support structure from an aftdirection; a retaining nut threaded into said main support structure forholding said bearing assembly therein, said threaded element beingrotatable from a radial direction whereby said turbine rotor may beremoved without disturbing said compressor.
 8. A gas turbine enginestructure as in claim 7 further comprising a compressor bearingtelescoped into the forward portion of said main support structure, saidcompressor rotor being telescopable into said compressor bearing from aforward direction; and a retaining clip restraining forward movement ofsaid compressor relative to said compressor bearing assembly wherebysaid retaining clip may be removed when said turbine rotor is removed topermit forward removal of said compressor rotor from said main supportstructure.
 9. A gas turbine engine structure as in claim 8 wherein saidcompressor bearing is telescopable against a shoulder in said mainsupport structure from a forward direction and is held therein by athreaded element.
 10. A gas turbine engine structure as in claim 9wherein said turbine is a centripetal turbine having radially extendingblades and said gas generator module comprisEs: a turbine inlet nozzleand shroud surrounding the periphery of said turbine for directing gasesinward across the blades of said turbine wheel; an annular turbine inletduct connecting with said inlet nozzle for directing a flow of hot gasestherethrough; said turbine inlet duct being removable in an aftdirection without disassembly of said inlet nozzle and said inlet nozzleand shroud being supported from said annular support structure radiallyoutward of the tip of said blades to permit removal thereof withoutremoval of said turbine.
 11. A gas turbine engine structure as in claim10 further comprising an annular heat shield positioned adjacent theback face of said turbine, said heat shield being sandwiched betweensaid annular support structure and said inlet nozzle and being splitwhereby removal of said inlet nozzle permits said heat shield to beremoved in a radial direction without disassembly of said turbine.
 12. Agas turbine engine structure as in claim 11 further comprising: aforward annular support structure positioned within said frame structureand journaling the forward portion of said compressor rotor, saidforward annular support structure being sandwiched between said gearboxmodule aft cover and said forward ring; and means for releasablyconnecting said forward annular support structure to said forward ringso that said gearbox may be removed from said engine withoutdisconnecting said forward annular support structure and said forwardring.
 13. A gas turbine engine structure as in claim 12 wherein saidreleasable connecting means comprises: a series of jury screwsconnecting only said aft cover and said gearbox housing; a series ofjury screws connecting said forward support structure and said forwardring; a series of jury screws connecting said annular support structureand said aft ring; a first set of threaded assemblies sandwiching thegearbox housing, the aft cover and the forward annular supportstructure, the forward ring; and a second set of threaded assembliessandwiching said aft ring, said annular support structure and said outerhousing.